The present invention relates to a control valve for hydraulic actuators or the like and including a valve casing or housing having a bore for receiving a valve slide element which in turn is subject to control of precontrol or actuator valves or the like.
Control valves of the type to which the invention pertains, are generally known and they are used primarily for controlling hydraulic actuators such as cylinders or the like. In these valves one employes a valve slide having annular ridges cooperating with annular grooves in the bore of the housing or casing for purposes of providing passing and/or no passing flow conditions. Upon shifting the valve slide, therefore, flow passages for the hydraulic fluid are either opened or blocked. Instrumental here are particularly the control edges as they are defined by the annular ridge or ridges in the slide and the groove or grooves in the casing or housing.
Hydraulic control valves are known which are also called four/three path valves. Such valves are usually moved into the desired control position by means of two electrically controlled precontrol valves. In this case one provides one precontrol valve per defined control position of the principal control valve in order to obtain two particular control positions of the slide. A third position is attained when none of the two precontrol valves are actuated which constitutes the idle normal or resting state. The two precontrol valves can be controlled only mutually exclusively which means that upon actuating one of the precontrolled valves the other one cannot be actuated. This however, is a drawback for the principal reason that at no time should a controlled or control element be subject to nonactuation i.e. effectively eliminated from the arrangement.